Make __libc_init_main_thread and android_set_abort_message weak

Bug: http://b/67672033
Bug: http://b/67934730
Test: make && flash and boot angler.
Test: run bionic-unit-tests
Change-Id: Ibf47f00dd7fae19014f56c857eb9712711363029
diff --git a/libc/bionic/android_set_abort_message.cpp b/libc/bionic/android_set_abort_message.cpp
index 8c80c5a..268c4f3 100644
--- a/libc/bionic/android_set_abort_message.cpp
+++ b/libc/bionic/android_set_abort_message.cpp
@@ -32,6 +32,7 @@
 #include <string.h>
 #include <sys/mman.h>
 
+#include "private/bionic_defs.h"
 #include "private/ScopedPthreadMutexLocker.h"
 
 static pthread_mutex_t g_abort_msg_lock = PTHREAD_MUTEX_INITIALIZER;
@@ -43,6 +44,7 @@
 
 abort_msg_t** __abort_message_ptr; // Accessible to __libc_init_common.
 
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
 void android_set_abort_message(const char* msg) {
   ScopedPthreadMutexLocker locker(&g_abort_msg_lock);